Spraying paint or the like media by means of compressed air



P. EssER 2,868,585 SPRAYING PAINT OR THE LIKE MEDIA BY MEANS OF' COMPRESSED AIR Jan. 13, 1959 Filed March 11. 1955 INVENTOR. Pff/UZ, 9555 BY f .inf/@Emery chamber.

United States Paten.,

SPRAYING PAINT OR THE LIKE MEDIA BY MEANS OF COMPRESSED AIR This invention `relates to a method of spraying paint and the like using a spray gun and to an improved spray -gun for carrying out the method.

It is known that paint and lacquer must be mixed with considerable amounts of thinners, in order to obtain a utilisable coat of paint. The thinners are more or less volatile, that is to say they have a certain rate of evaporation, which dilers according to the particular thinner used.

Innormal paint spray guns, the mixture is so distributed, by the iine distribution of the paint thinning medium mixture which is ejected by means of compressed air from the outlet nozzle or mouth ofthe gun, in such manner that a mass of these paint thinning medium particles mixed with paint passes into the spraying space and thus forms the detrimental paint mists which soil the surroundings. Depending on the rate of evaporation and amount of thinners used, these paint mists remain in the space until the thinner has evaporated from the particles of paint, and the latter drop down. They must therefore be exhausted since otherwise they would be inhaled by the operator. The consequent danger to the health of the operator has, in most countries, led to a complete prohibition of the use of various media, for example red lead, for the purpose of spraying.

The present invention aims at obviating the foregoing disadvantages of previously known spraying methods. It has been found, and conrmed by practical experiment, that the formation of mist can be completely suppressed if the injector action hitherto used is avoided and a new spraying method used, which consists in that the medium to be sprayed, the compressed air are intimately mixed with one another and whirled up before passing out of the nozzle or outlet passage, that is to say while still inside the gun. If the gun has a so-called mixing chamber or mixture-receiving chamber, it is advisable to mix the air and paint before they enter the mixing-receiving Thus, pre-mixed air and paint enter the socalled mixing chamber, which actually functions as a receiving chamber for the pre-mixed air and paint.

Whereas with the previously used injector method air bubbles were produced which, like a soap bubble, were surrounded by a skin of paint and tended to be distributed i in space away from the nozzle, according to the invention very nely divided droplets of paint are produced which are surrounded by a thin skin of air and when the ratio of the mixture of air and paint is correctly adjusted are immediately deposited on the object to be sprayed without forming mist.

The advantages of the method of the present invention are obvious; in the irst place exhaust booths or the like equipment can be dispensed with; losses of paint, lacquer and thinner are substantially completely avoided; the surroundings are not soiled and operators suffer no hindrance. It has further been found that even highly volatile substances such as acetone, carbon tetrachloride, benzine, alcohol, and similar media do not form a mist. Even ,y 2,868,585 Patented Jan. 13, 1959 red lead can be sprayed without danger, because the hitherto existing risk .of injury to health is eliminated. Most ready-mixed brushing paints and lacquers can be sprayed without adding further thinners, so that there can also be a saving in respect of thinning. In consequence of the novel formation of the paint-air particles, the paint is applied satisfactorily and covers well, 4forming a tighter seal, which is more uniform and economical.

In order to eifect the intimate mixing of paint and compressed air, the compressed air passage can be brought into the paint passage at an4 acute angle ofA preferably about 60.

It is however more advantageous for the paint passage to lead into the compressed air passage. The air iiowing through the air passage seizes the paint or the like (the amount of which may be regulated) entering the cornpressed air passage from the paint rising pipe in such an amount that the coating is applied uniformly to the part to be sprayed without forming drops.

The invention also consists in a spray gun for carrying the foregoing method into practical eiect wherein passages are provided in the gun for compressed air and spraying medium, said passages merging into one another before reaching. the spraying nozzle or outlet.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example, three embodiments of spray guns in accordance therewith, and in which:

The single ligure of the drawing shows a View, partly in side elevation and partly in section, of one embodiment of paint spray gun according to the invention.

ln the construction of spray gun shown in Figure '1, the gun body 10 formed at one end with a raised portion lil is, mounted on a paint container 11, a supply tube 12 being immersed in the paint container to a point near the bottom of the container.

Compressed air is supplied to the gun body through a passage 17 in the control handle member 13, while a valve 15 controlled by means of a trigger 14 opens or closes `the passage 17. The compressed air supply runs from the valve l5 through a bore 16 into a longitudinal passage 18 in the gun body 10, the free end of which passage is directed obliquely upwards at 18 as an angular extension at an acute angle and leads into a mixture receiving chamber 19 having an axis parallel to the longitudinal gun body. The paint supply pipe 12 leads from below through another passage in the gun body into angular extension 18 of the longitudinal passage 18 at a substantially right angle thereto, so that the paint and air are already mixed inside the gun body and the airpaint mixture enters the mixture receiving chamber 19 in a mixed state, and in said chamber a final whirling up takes place before the mixture passes out through the spray nozzle 21, which is closeable by a needle valve 22 which is likewise operated by the trigger 14.

20 is a valve which controls the amount of compressed air flowing through the passage 18, and 23 is a valve which controls the amount of paint iiowing through the` tube 12. In addition, a tube 20 branches oif from the compressed air pipe 18 and ends in the paint container above the surface of the paint and in known manner produces the delivery pressure on the paint surface, by which the latter is forced into the pipe 12.

The invention is not restricted to the forms of construction illustrated and described, but on the contrary many other forms of construction and applications are possible within the scope of the appended claim, particularly with regard to structural modifications of the construction of the gun and the arrangement of the cornaaeaese pressed air passage on the one hand and on the other hand also with regard to the media to be sprayed, of which paint is only one example of application. Thus, in addition to paint, lacquers, acetone, carbon tetrachloride, benzine-,"'alcohol', anti-rust medium, and similar sprayable substances can also be atomised with the new mist-free spray gun. In order to spray with the gnn media which cannot be thinned, and in order to dry sprayed coating immediately, the container lll can be heated. At the asme time the air can also be heated by a heating unit situated before the connection branch..

What I claim is: A spray gun adapted to engage with the open end of a uid container comprising, anV elongated gun body formed at one end with a raised portion having a mixtr e receiving chamber Whose axis extends parallel to said elongated gun body; a spray nozzle secured forwardly ot said raised portion and communicating with said mixture receiving` chamber; said elongated gun body having a irst passage extending longitudinally therethrough for introdacing compressed air into the gun body; valve means mounted in said rst passage for regulating the llow of such air; a second passage in said gun body substantially perpendicular to said lirst passage for permitting the flow of iiuid into said gun body; valve means mounted in said second passage for regulating the flow of such iiuid; a supply tube connected to said gun body in uid communi* cation with said secondpassage and adaptedfor immer sion in a iuid-lled container; said rst passage having an angular extension communicating with said second passage and extending into said mixture receiving chamber, said angular extension being disposed at an angle with respect to the axis of said mixture receiving chamber; a pressure tube element connected to said first passage and adapted to extend into the fluid container; a control handle member forming a part of said gun body; a needle valve element extending axially through` said' r'eceiving chamber into said control handle and having a needle portion normally engaging and closing said-spray-nozzle; a trigger pivotally secured to said handle and operatively engaging said needle valve, said handle having an air inlet passage therein communicating with said first passage; a valve mounted in said inlet passage, said valve having a stem in operative engagement with said trigger.

References Cited in the le of this patent UNlTED STATES PATENTS 

